Data centres are formed by large rooms or buildings, inside of which there is an important number of electronic equipment intended to process the information of a particular company or organization. This type of centres requires high energy consumption, which is currently divided into approximately the following way: electronic equipment 38%-63%, air conditioning 23%-54%, uninterrupted power supply (UPS) 6%-13% and lighting 1%-2%, among other less important facilities. Besides, it is estimated that cost associated to said energy consumption increases annually between 10% and 25%.
The consumption corresponding to air conditioning equipment is particularly significant, since it has great influence on the PUE (Power Usage Effectiveness) coefficient. This coefficient is expressed as the relation between the energy intended to data processing and the total energy consumed by the data centre. The closer to 1 the value of said coefficient is, the greater the harnessing of the energy consumed by the data centre will be. However, the consumption intended for air conditioning equipment often considerably penalizes the PUE value. For example, mean PUE values can be found close to 1.05, when refrigeration systems are used through natural ventilation, close to 1.6 in newly installed data centres using conventional refrigeration systems, such as refrigerant gas-air, water-air, and up to 2.5 and 3 in existing data centres with this type of systems. Other coefficients which are also negatively affected by more conventional refrigeration systems are CAPEX and OPEX. The former refers to capital expenditures, while the latter refers to operation expenditures.
Nowadays, therefore, there exists a growing interest in reducing the consumption of data centre conditioning systems. In this sense, there are known the following solutions.
The first of them consists of the use of systems based on direct natural ventilation of data centres, which could be used to obtain PUE values very close to 1. However, this solution has multiple inconveniences.
First, there exists the air pollution problem. Specifically, the inner space conditions of a data centre are so demanding that they require the installation of air filters in order not to damage the electronic equipment and reduce their life. However, air filters produce a certain percentage of efficiency loss in the system, which increases progressively as they become dirty. Therefore, it is necessary to provide constant system maintenance and periodically substitute the dirty filters.
Another problem of natural ventilation systems is the lack of control of the relative humidity inside the inner space of the data centre, which according to existing regulations, such as ASHRAE, and to the requirements of electronic equipment manufacturers reaches adequate values close to 50%.
The high risk of water presence inside the data centre is also one of the important problems of natural ventilation systems. Water is a critical element in a data centre, being very harmful to electronic equipment and the correct operation thereof. Natural ventilation requires openings which communicate the outer space with inner space of data centres, which constitute a water access point. In order to avoid these undesired infiltrations, there are often used filters, pent roofs or even external covers, or other buildings or industrial units inside of which the data centre is located.
Finally, another problem of natural ventilation is that it can only be applied in certain geographical areas, where outside temperatures are low enough all year round for the correct operation of the data centre. Thus, natural ventilation systems normally form part in many occasions of mixed systems, that is, systems which combine natural ventilation with conventional air conditioning facilities, to enable the application of a greater number of geographical areas.
Another one of the solutions known to reduce the consumption of environment conditioning systems of data centres can be found in EP1903849A1. This document shows an environment conditioning system of the inner space of a data centre which uses a rotating air-to-air heat exchanger, configured to facilitate heat exchange between an outer air flow and a recirculation air flow coming from the inner space of the data centre. This type of exchangers is usually formed by a large rotating cylinder constituted by metal plates of great density. Its operation is based on the thermal inertia of the materials constituting it, so that they absorb and retain the heat of the recirculation air flow and transfer it to the outer air flow as the cylinder rotation takes place. This solution also has multiple inconveniences.
First, said solution does not guarantee 100% the presence of cross-contamination between the aforementioned flows. Although it can be seen that the exchanger is located between two separated air chambers, being half of it in each one of them, there exists no possible separation along its diameter length and width. Therefore, the pressure differences between both flows always produce a cross-contamination minimum. For the same reason, it cannot be guaranteed the absence of water coming from the condensation on metal plates, which passes to the recirculation air flow, and it is not possible to carry out a thorough control of the relative humidity of the inner environment.
However, the greater inconveniences of this system are the need to maintain the exchanger continuously moving and the important energy consumption required by the engine configured to that end, taking into account the great weight and volume of these exchangers. The first of these inconveniences forces to have similar redundant auxiliary measures which guarantee the continuity of the operation, so necessary in data centres. In this sense, it is necessary to have at least one back-up engine and dual power supply intended to produce the movement. On the other hand, the second of these inconveniences directly affects the system energy efficiency, since the engine consumption and its associated components have a negative effect on the PUE.
The high energy efficiency system for the air conditioning of the inner space of a data centre of the present invention solves the aforementioned problems in a fully satisfactory manner. Specifically, the system of the present invention uses a passive air-to-air heat exchanger, free of moving elements, configured to allow heat exchange, without air cross-contamination, between the outer air flow and the recirculation air flow. Wherein said system also enables the recovery of heat dissipated by data processing electronic equipment for its later harnessing, and it is also complemented by other elements which allow the system operation in a wide range of geographical areas with very different climates.